I was working on a JD LA115 with 31 Cu in Briggs that had sat at least two years. Long enough there was multiple problems that had to solve before final repairs.
The engine started on the fuel in the tank so I kinda figure it just a fresh dump by the owner attempting to start it before they sent the mower in. Apparently not the case. The engine ran fine off load other smoking due oil in the cylinder and muffler. The problem showed up under the deck load. When you first engage the engine struggled and knock heavily until back up to full speed. Considering this was Intek I pulled the rocker cover and did a leak down test checking a blown head gasket which it passed other finding a crappy installed plug wire terminal. So adjusted the valves and resealed the rocker cover. For some reason it dawn on me to drain the fuel and replace with known good fuel. Maybe it was that mower had sat two years and in the back of mind the fuel could be a problem.
After the RTV had set up I crank up the engine with the new fuel and the struggling and knocking was cured. Apparently I had a case of pre-ignition with old fuel. To be honest it is the first time I have ran across this particular problem. Oh I had lot of bad fuel cases in the 15 yrs I have been doing this work professionally but none like this one.
Has anyone else ever ran into this particular problem? Usually here when the is bad it is bad all the way.
Hi AVB, Yes I have experienced this issue with vintage motorbikes but not with mowers, I usually never trust fuel in anything that has been sitting for a while
Now I don't feel so alone...In a way I just got lucky that I did the leak down test instead just pulling the head for a head gasket replacement. But these Briggs single cylinder Intek are bad about blowing head gaskets and I have learn to do the leak downs while I have rocker cover just check them.
And just shows you are never too old or too experienced not to learn something new by being thrown a new curve ball.
As for the gasoline every DIY tech barks its because of ethanol fuel use but even what they call pure gasoline has its own breakdowns. I can walk by cars that been storage for a long as they smell like old paint at times and know they have bad gasoline.
Yes AVB, My son was over from NZ a few weeks ago and he wanted my 65 Enfield Interceptor and CB Honda started because they hadn't been started since he was here before covid started 4 years ago. Even though I hadn't run the fuel out of the carbs 4 years ago ( silly move) but with fresh fuel the Inter started on the 4th kick. The Honda took a bit more persuading but with a bit of starter fluid it eventually fired up on four cylinders and settled down to run nicely. I must put more effort into keeping them fired up more regularly.
I've had the old fuel problem many times,I think it's a lot more noticeable with bigger engines than if you had old fuel in a 3.5 briggs.
I've had a few old cars given to me that were sitting not run for years and drained the old fuel out and as long as the fuel burns and it usually stinks like old paint thinners I would use the fuel in an old car with a single Stromberg carby as long as you go for a drive the same day you put the fuel in and burn it all up you can use it , the only problem was the old fuel has lost octane and lost some volatility, the lower the octane rating fuel burns more quickly while higher-octane fuels burn more slowly so because the old fuel now burns quicker because of reduced octane the motor will have a tendency to knock more and when you turn the motor off they can run on (dieseling).
I have bikes here that I sometimes haven't run them for a while and it's always annoying that I have to pull the carby off and clean it out to get the bike running again.
That's why I prefer LPG ,I have an old Ford here that wasn't started sat in the same spot for 10 years ,it's on LPG ,I wanted it moved the other day so I primed the gas, took the air cleaner lid off sprayed a little 2 stroke fuel down the carby and it fired straight up.
Have another LPG car that wasn't started for a year and that had no problem starting but the LPG in the tank would be about 4 years old.
The only other uses for old fuel I find is for washing parts or sometimes I use it in a spray bottle and spray the ants on brick paths and it's good to put down ants nests and then burn (one way to turn ants into fire ants), works better than an ant surface spray.
I still have some leaded fuel and that was phased out in January 2002 but it still works in mowers and starts easily but when I have some old unleaded it won't even run in a mower and old unleaded completely rusts the tank if left for too long.
Now we over here do have an ant we call fire ants. Their stings burn like fire plus they bite and you definitely do not want step on their mounds as they can quickly cover you up. Destroying them is the only to control them. An invasive species. And according to the research here you also have them.
Not nearly as bad here at the new place but they are here. At the old place I had war with them and it was nearly a stalemate. Sometimes I was winning and other times I was losing.
I was burning the tiny ants but we also have in Australia one of the largest and most aggressive species of ants on the planet AVB.
Myrmecia are often called bulldog ants, bull ants, inch ants, sergeant ants, or jumper ants,they are so aggressive if you cut them in two, the head and the tail will actually fight and seek to kill each other.
Ants as old as dinosaurs and if you throw them out of a plane they won't die because their terminal velocity is only 4 mph.
Lots of different ways to exterminate ants with a search though.
And we also have Bluebottles, that is what we used to call them, look the same as the Bull ant but bright blue. I only occasionally see a Bull ant and haven't seen a Bluebottle for years here, but they are mostly found in the bush. They are a nasty piece of kit and stomping on them will not kill them unless it is on concrete and then you have to twist you foot on them to squash them
